Halo-substituted thionoacyl ketone herbicidal antidotes

ABSTRACT

Compounds having the formula ##STR1## in which R and R 1  are each haloalkyl having 1-4 carbon atoms have utility as herbicidal antidotes.

BACKGROUND OF THE INVENTION Uses of Herbicides

A herbicide is a compound which controls or modifies plant growth, e.g., killing retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating, dwarfing and the like. Plant refers to all physical parts, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage and fruits. Plant growth is meant to include all phases of development from seed germination to natural or induced cessation of life.

Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control can increase crop yield and reduce harvesting costs.

Herbicidal effectiveness is dependent upon several variables. One of these is the time or growth related method of application. The most popular methods of application include: pre-plant incorporation into the soil; pre-emergence surface treatment of seeded soil; and post-emergence treatment of the plant and soil.

The most important determinant of herbicidal effectiveness is the susceptibility of the beneficial crop and selectivity toward weeds. Certain herbicidal compounds are phytotoxic to some weed species but not to others.

A manufacturer of a herbicide generally recommends a range of rates and concentrations calculated to maximize weed control. The range of rates usually varies from approximately 0.1 to approximately 50 pounds per acre (lb/A) [0.112 to 58 kilograms per hectare (k/ha)], usually from 0.1 to 25 lb/A (0.112 to 26 k/ha). The actual amount used depends upon several considerations, including, crop tolerance, particular weed susceptibility and overall cost limitations.

Some herbicides display exclusive selectivity toward weed species. Many are toxic to both weeds and the intended crop beneficiary. Therefore, a particular herbicide may proscribe its injurious effect on the cultivated crop even though it may otherwise provide excellent control of weeds found in the crop field.

To preserve the beneficial aspects of herbicide use and to mitigate crop damage, many herbicidal antidotes have been prepared. These antidotes reduce or eliminate damage to the crop without substantially impairing the beneficial effect of the herbicide. For example, see U.S. Pat. Nos. 4,021,224 and 4,021,229 and Belgian Pat. No. 846,894.

Although several explanatory theories have been advanced, the precise mechanism by which an antidote reduces herbicidal crop injury while retaining weed injury has not been conclusively established. An antidote compound may in fact be a remedy, interferent, protectant, or antagonist. As used herein, antidote describes, i.e., the continued effect of establishing herbicidal selectivity of herbicidal phytotoxicity to weed species and reduced or non-phytotoxicity to cultivated crop species.

As an alternative mode of action, the compounds of this invention may interfere with the normal herbicidal action of the thiolcarbamate-type herbicides to render them selective in their action. Whichever mode of action is present, the corresponding beneficial and desirable effect is the continued herbicidal effect of the thiolcarbamate with the accompanying decreased herbicidal effect on desired crop species. This advantage and utility will become more apparent hereinafter.

Therefore, the terms herbicide antidotes or antidotal amount is meant to describe that effect or the amount which produces the effect which tends to counteract the normal injurious herbicidal response that the herbicide might otherwise produce. Whether it is to be termed a remedy, interferent, protectant, or the like, will depend upon the exact mode of action. The mode of action is varied, but the effect, which is desirable, is the result of the method of treating the soil in which a crop is planted.

Thiolcarbamate herbicides are particularly effective in the control of grassy type weeds which interfere with the cultivation of a wide variety of crops, e.g., barley, corn, lentils, peanuts, peas, potatoes, soybeans, spinach, tobacco and tomatoes. Frequently, the beneficial use of the thiolcarbamates can be enhanced by the addition of an antidotal compound.

DESCRIPTION OF THE INVENTION

It has been discovered that certain thionoacyl ketone compounds are effective antidotes for the protection of corn from thiolcarbamate herbicidal injury. Such compounds have the formula ##STR2## in which R and R₁ are each haloalkyl having 1-4 carbon atoms, preferably trifluoromethyl.

This invention is a herbicidal composition comprised of

(a) a non-phytotoxic antidotally effective amount of a thionoacyl ketone compound of the formula ##STR3## in which R and R₁ are each haloalkyl having 1-4 carbon atoms, preferably trifluoromethyl; and

(b) a herbicidally effective amount of a thiolcarbamate of the formula ##STR4## in which R₂ is selected from the group consisting of alkyl having 1-6 carbon atoms and alkenyl having 2-6 carbon atoms;

R₃ is selected from the group consisting of alkyl having 1-6 carbon atoms, alkenyl having 2-6 carbon atoms, cyclohexyl and phenyl; or

R₂ and R₃ together form an alkylene group having 5-10 carbon atoms; and

R₄ is selected from the group consisting of alkyl having 1-6 carbon atoms, haloalkyl having 1-4 carbon atoms, cycloalkyl having 5-10 carbon atoms, phenyl, substituted phenyl, wherein the substituents are alkyl having 1-4 carbon atoms, haloalkyl having 1-4 carbon atoms, and halo, benzyl and substituted benzyl, wherein the substituents are alkyl having 1-4 carbon atoms, haloalkyl having 1-4 carbon atoms and halo.

The terms alkyl and alkenyl as used herein are intended to include both straight- and branched-chain groups. The term halo is intended to include mono- and polyhalo groups and includes, chloro, bromo, iodo, fluoro and mixtures thereof. All carbon atom ranges are intended to be inclusive of both upper and lower limits. Exemplary of alkyl are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiarybutyl, pentyl, hexyl and the like. Exemplary of alkenyl are such groups as vinyl, propenyl, butenyl, pentenyl, hexenyl and the like. Exemplary of cycloalkyl are cyclopentyl, cyclohexyl, 2,2 dimethyl cyclohexyl, cycloheptyl and the like.

By way of exemplification, the active thiolcarbamate herbicides employed in the invention may include the following: EPTC, S-ethyl diisobutyl thiocarbamate, S-propyl dipropyl thiocarbamate, S-2,3,3,-trichloroallyldiisopropyl thiocarbamate, S-ethyl cyclohexyl ethyl thiocarbamate, S-ethyl hexahydro-1H-azepine-1-carbothioate, S-4-chlorobenzyl diethyl thiocarbamate and combinations thereof.

This invention also includes the method of protecting crops from herbicidal injury which comprises applying to the locus where protection is desired an antidotally effective amount of a thionoacyl ketone compound of the formula ##STR5## in which R and R₁ are each haloalkyl having 1-4 carbon atoms, preferably trifluoromethyl.

Preparation

The thiocarbamates of the present compositions can be prepared by the procedures described in U.S. Pat. Nos. 2,913,327, 2,983,747, 3,133,947, 3,185,720 and 3,198,786. 1,1,1,5,5,5-Hexafluoro-monothiono-acetyl acetone which is representative of the thionoacyl ketone compounds of this invention, is commercially available.

Testing

Stock solutions of the herbicides are generally prepared by diluting the requisite amount of the formulated herbicide in water. The solution compositions and application rates are summarized in Table I.

                  TABLE I                                                          ______________________________________                                         Herbicide Stock Solutions                                                                 Composition                                                                    Herbicide                                                                              Water   Application                                         Herbicide Name                                                                              (mg)      (ml)    ml/flat                                                                              ˜                                                                            lb/acre                               ______________________________________                                         EPTAM® 6E                                                                               27        50      5         0.50                                  S-ethyl N,N- 267       50      5         5.00                                  dipropylthiocarbamate                                                          ______________________________________                                    

Stock solutions of the antidotes were prepared by diluting the requisite amount of the compound in acetone. The compositions and application rates appear in Table II.

                  TABLE II                                                         ______________________________________                                         Antidote Stock Solutions                                                       Composition       Application                                                  Antidote (mg)                                                                             Acetone (ml)                                                                              ml/flat ˜                                                                            lb/acre                                                                              Method*                                ______________________________________                                         1,1,1,5,5,5-Hexafluoro-monothio-acetyl acetone                                 Stock A:                                                                       200        50         5.0         5.00  PPI                                    Stock B:                                                                       1 ml of A  99         5.0         0.05  PPI                                    ______________________________________                                          *PPI = Preplant incorporation of antidote and herbicide.                 

All of the soil used in the tests described herein was loamy sand soil treated with 50 parts per million (ppm) each of a commercially available fungicide, N-[trichloromethyl)thio]-4-cyclohexene-1,2-dicarboximide, and 18-18-18 fertilizer, which contains 18% by weight equivalent each of nitrogen, phosphorus pentoxide, and potassium oxide.

The herbicides and antidotes were applied to the soil by pre-plant incorporation (PPI) into the soil prior to seeding.

After planting, all flats were placed on greenhouse benches where temperature was maintained between 70° to 90° F. (21.1° to 32.2° C.). The flats were watered by sprinkling as needed to assure good plant growth.

Control flats contained crops treated with herbicides only at the various rates.

Injury ratings were taken four weeks after application of the antidote. The effectiveness of the antidote was determined by visual comparison of injuries to crops and weeds in the control and test flats to those in untreated flats.

The treated crops initially screened for diminution of herbicidal injury were milo, wheat, cotton, rice, barley, corn and soybeans. The herbicide-antidote compositions were tested for control of foxtail (Setaria viridis).

The representative antidote compound, 1,1,1,5,5,5-hexafluoro-monothiono-acetyl acetone, when applied preplant incorporated at the rate of 5.0 lb/A and the representative thiolcarbamte herbicide, EPTC (S-ethyl-N,N-dipropyl thiolcarbamate), was applied preplant incorporated at the rate of 5.0 lb/A completely protected corn (Zea Maize) from phytotoxic injury the untreated flat with EPTC alone displayed 97% injury to the corn, when treated with the herbicide plus antidote compound no injury (0%) occurred.

The weed species Foxtail (Setaria viridis) in the treated and untreated flats exhibited 98% injury; with no protection from the thiolcarbamate herbicide by the antidote compound.

Formulations

The object of the formulation is to apply the compositions to the locus where control is desired by a convenient method. The locus may include soil, seeds, seedlings and vegetation.

The amount of antidote compound which comprises part of a herbicidal composition will generally range from approximately 0.001 to 30 parts by weight per weight of the herbicidal compound.

Formulations will generally contain several additives. Among these are inert ingredients, diluent carriers, organic solvents, water, oil and water, water in oil emulsions, carriers of dusts and granules, and surface active wetting, dispersing and emulsifying agents. Fertilizers, e.g., ammonium nitrate, urea and superphosphate, may also be included. Aids to rooting and growth, e.g., compost, manure, humus, sand, etc., may likewise be included. The formulations are commonly dusts, wettable powders, granules, solutions or emulsifiable concentrates.

Dusts are free-flowing powder compositions containing the herbicidal compound impregnated on a particulate carrier. The particle size of the carriers is usually in the approximate range of 30 to 50 microns. Examples of suitable carriers are talc, bentonite, diatomaceous earth and pyrophyllite. Anti-caking and anti-static agents can be added, if desired. The composition generally contains up to 50% of active ingredient. Dusts, like liquid compositions, can be applied by spraying from boom and hand sprayers or airplanes.

Wettable powders are finely divided compositions comprising a particulate carrier impregnated with the herbicidal compound and additionally containing one or more surface active agents. The surface active agent promotes rapid dispersion of the powder in aqueous medium to form stable, sprayable suspensions. A wide variety of surface active agents can be used, for example, long chain fatty alcohols and alkali metal salts of the sulfated fatty alcohols; salts of sulfonic acid; esters of long chain fatty acids; and polyhydric alcohols; in which the alcohol groups are free, omega-substituted polyethylene glycols of relatively long chain length. A list of surface active agents suitable for use in agriculture formulations can be found in Wade Van Valkenburg, Pesticide Formulations (Marcel Dekker, Inc., N. Y., 1973) at pages 79-84.

Granules comprise the herbicidal composition impregnated on a particulate inert carrier having a particle size of about 1 to 2 millimeters (mm) in diameter. The granules can be made by spraying a solution of the active ingredient in a volatile solvent onto the granular carrier. Suitable carriers in preparation of granules include clay, vermiculite, sawdust, granular carbon, etc.

The herbicidal compositions can also be applied to the soil in the form of a solution in a suitable solvent. Solvents frequently used in herbicidal formulations include kerosene, fuel oil, xylene, petroleum fractions with boiling ranges above xylene, and aromatic petroleum fractions rich in methylated naphthalenes.

Emulsifiable concentrates consist of an oil solution of the herbicide along with an emulsifying agent. Prior to use, the concentrate is diluted with water to form a suspended emulsion of oil droplets. The emulsifiers used are usually a mixture of anionic and nonionic surfactants. Other additives such as spreading agents and stickers can be included in the emulsifiable concentrate.

The compounds and compositions of this invention can also be applied by addition to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein.

It is not necessary that the compounds and compositions be admixed with the soil particles. After application by the above discussed methods, they may be distributed below the surface to a depth of at least one-half inch by conventional means such as discing, dragging or mixing. 

I claim:
 1. A herbicidal composition consisting essentially of(a) a non-phytotoxic antidotally effective amount of a compound of the formula ##STR6## and (b) a herbicidally effective amount of a thiolcarbamate herbicide of the formula ##STR7## in which R₂ is selected from the group consisting of alkyl having 1-6 carbon atoms;R₃ is selected from the group consisting of alkyl having 1-6 carbon atoms, and cyclohexyl; or R₂ and R₃ together form an alkylene group having 6 carbon atoms; and R₄ is selected from the group consisting of alkyl having 1-6 carbon atoms, 2,3,3-trichloroallyl, and chlorobenzyl wherein said antidote compound is present in an amount ranging between about 0.001 to 30 parts by weight for each part by weight of the thiolcarbamate herbicidal compound.
 2. A composition according to claim 1 in which R₂ and R₃ are each propyl and R₄ is ethyl.
 3. A method of controlling undesirable vegetation while reducing herbicidal injury to crops due to thiolcarbamate herbicides which comprises adding to the soil a non-phytotoxic antidotally effective amount of a compound of the formula ##STR8##
 4. A method of controlling undesirable vegetation while reducing herbicidal injury to crops due to thiolcarbamate herbicides which comprises adding to the soil a non-phytotoxic antidotally effective amount of a compound of the formula(a) a non-phytotoxic antidotally effective amount of a compound of the formula ##STR9## and (b) a herbicidally effective amount of a thiolcarbamate herbicide of the formula ##STR10## in which R₂ is selected from the group consisting of alkyl having 1-6 carbon atoms;R₃ is selected from the group consisting of alkyl having 1-6 carbon atoms, and cyclohexyl; or R₂ and R₃ together form an alkylene group having 6 carbon atoms; and R₄ is selected from the group consisting of alkyl having 1-6 carbon atoms, 2,3,3-trichloroallyl, and chlorobenzyl wherein said antidote compound is present in an amount ranging between about 0.001 to 30 parts by weight for each part by weight of the thiolcarbamate herbicidal compound. 